A CMOS image sensor may be divided into a photo diode region for receiving light signals to convert them into electric signals, and a transistor region for processing the electric signals. CMOS image sensors may have a structure where the photo diode is horizontally disposed relative to the transistor. Of course, although the disadvantage of a CCD image sensor may be overcome by using a lateral CMOS image sensor, the lateral CMOS image sensor still has its disadvantages. In other words, with a lateral CMOS image sensor, the photo diode and the transistor may be manufactured to be horizontally adjacent to each other on a substrate. Therefore, an additional region for the photo diode is required, thereby causing problems by reducing a fill factor region and limiting the possibility of resolution. Also, the lateral CMOS image sensor is very difficult to accomplish optimization during a process for simultaneously manufacturing the photo diode and the transistor.